Interference elimination



A. HUBNER INTERFERENCE ELIMINATION M/BZ M i T I INVENTQR) 9ERED HUBNER Patented Oct. 9, 1928.

U NlT-ED STATES P rENroFFlfca.

Hl IBNER, OF IBERLINJ'RIEDENAU, GERMANY, ASSIGNOR TO SIEMENS d. HALSKE, OI BERLIN, GERMANY, A CORPORATION OI GEBKANY INTERFERENCE ELIMINATION.

Application filed. December a, 1926, Serial No. 153,227, and in Germany mm :1, 1925.

This invention relates to interference elimination, and more particularly to a method and means for neutralizing the effect of interference on either a receiving or a\ stray actions are caused, for. instance, by,

electric railways, potential variations 1n 7 power lines due to the connection and disconnection of consumers, the influences of other electrical apparatus such as'magnetos, Roentgen-ray apparatus, and the like. It has already been suggested to rotect radio apparatus from the eifect o suchv stray waves by the provision of filter circuits and the like, but this is profitably possible only to a certain extent, because there always remains a relatively large residual action upon the thermionic tubes of receiver and transmitter apparatus.

Now, the present invention relates to a method by means of which it is possible to preclude disturbing stray actions of extraneous waves to a large extent, or even completely. According to the invention, the disturbing impulses coming to act upon the receiving or transmitting thermionic tubes are extinguished by what'may be called counter impulses which are produced by another thermionic tube which is also subject to the action of the disturbing electrical waves."

Such an equipment is illustrated by way of example in the accompanying drawing, in which Figure 1 shows diagrammatically the circuit arrangement used in my invention, and 1 Figures 2 and 3 show modifications of the arangement shown in. Figure 1.

Referring to the drawing, 1 is the thermionic tube of a radio receiver, which is acted upon by the antenna 3 through the condenser 2. 4 is the plate battery, 'while 5 is the telephone. Now, the grid of tube 1 is acted upon not only by the waves to which the aerial is tuned, but also by disturbing impulses having other wave-lengths. At 7, as will be noted, a lead 8 is branched off from the lead brought to the grid of tube 1, said branch lead being-brought by way of an excluding or rejector circuit 9 and lead 10 to the grid of the tube 11. The purpose of circuit 9 which includes an inductance and variable capacity is to exclude ,in potential occurs Whic waves of the si [a1 frequency from the grid of tube 11. Y e. tube 11 contains te glate battery 13 and a high resistance 14. he plate member of this tube '11 is'connected to the grid of tube late circuit of the said,

1 through the lead 15 and a condenser 16.

, The operation of the scheme is as follows: Upon the reception of waves having that wave len th to which both the antenna and the exclu ing or rei'ector circuit 9 are tuned, the antenna 3 wil not affect the tube 11, since these waves, as stated, are precluded by the re'ect'or circuit 9 from the grid of tube 11; ence, a uniform and stable potential will be set up between plate and filament of the tube 11, which potential is blocked by the condenser 16, hence no actionupon the control of tube 1 by the tube 11 is brought about. Now, to study the effect of a disturbing wave train, let us suppose a simple rise is transmitted to the lead to the grid of tube 1. Such an impulse of potential will pass thru the rejector circuit '9 and lead 10 and so, will also'act upon the grid of the tube 11, causing a posi- "tive increase in potential; In conse uencc the resistance of tube 11 is diminishe corplate and filament of this tube is likewise reduced, this being brought about by the influence of the plate resistance 14. This reduction in potential will act thru conidenser 16 upon the grid of the tube 1, as a potential reduction, which, provided all of the electribal quantities have been properly adjusted,-will compensate or neutralize the original'potential rise. Of course, the actual disturbance will be more in the nature of atrain of Waves. By inaccurateadj'ustment the interfering wave may be even overcompensated.

Of course, careful selection of the tube 11 and of the magnitudes of the resistances,

.respondingly, so that the potential between inductances and capacities must be made to attain exact compensation or neutralization. Under certain circumstances, even a second or a third tube may be resorted to, for the purpose of insuring neutralization of the ,stray waves, and these, if desired or necesbatteries and the like, have for the sake of simplicit been omitted.

Instea of influencing the grid of tube 1 directly by means of the supplementary or auxiliary tube, such influences may be applied upon the plate circuit of tube 1, as shown in Fig. 2.

In this modification the disturbing wave train causes for example a positive increase of potential on the grid of tube 11, which will decrease the resistance of tube 11 and cause a reduction of potential on the plate thereof. This reduction'in potential causes -by means of the amplifying relay 11' an increase of potential in the platecircuit of tube 11' and consequently on the plate circuit of tube 1 to which it is connected The same disturbing wave train causes a positive increase of potential on the grid of tube 1' which will cause a reduction in potential on the plate of tube 1. This decrease in potential on the plate of tube 1 will be neutralized or compensated by the increase in potential set up on the plate of tube 1 by the disturbing'wave train acting through tubes 11 and 11 as pointed out above. By properly selecting the tubes 11 and 11 and associated resistances theefiect of a disturbing wave train can be exactly neutralized or compensated, and will not interfere with the received signals.

The selector need not be the rejector circuit 9, for any other device or means may be employed which will preclude the desired wave from the grid of tube 11.

Tube 11, of course, may be supplied with control current from a separate antenna, as in Fig. 3. The modification shown in this figure operates in the same manner as the device shown in Figure 1 except that a separate antenna is used to supply the grid of tube 11 with the disturbing signals.

The means here disclosed are serviceable both for the protection of transmitter as well as of receiver apparatus against stray or interfering waves.

Each of the above disclosed arrangements besides preventing interference also insure a high degree of selectivity.

I claim:

1. In combination, an antenna circuit,'two electron emission tubes having control 'elec,- trodes, one of said control electrodes being connected to said antenna. through a con-.

denser, the other of said control electrodes being connected to the antenna through a parallel resonant circuit adapted to block second electron tube having its input circuit coupled to said antenna through saidthe desired frequency, and capacitive means parallel 1 resonant circuit, and capacitive means coupling said electron tubes in phase opposition.

3. In combination, first electron tube having its input circuit coupled to said antenna, a parallel "resonant circuit tuned to an operating frequency, a.

second electron tube having its input circuit coupled to said antenna through said parallel resonant circuit, an output circuit for said second tube, an impedance in said output circuit, and means including ablocking condenser to connect said output circuit to the input circuit of the first tube.

an antenna circuit, a

4. In radio apparatus, an antenna, an in- I 'ductance and capacity in series therein, a

vacuum tube having input elements, means includin a condenser for connecting said input e ements across said inductance, a second vacuum tube having input and output elements, means includmg an operating frequency rejector circuit for connecting said last named input elements across said inductance, an output circuit including a resistance for said .second named tube, and

means including a condenser for'coupling the output circuit of said last named tube to the input circuit of said first named tube.

In testimony whereof I aifix my signature.

ALFRED Hi'IBNER. 

